1. Field of the Invention
This invention relates generally to a communication network and in particular to providing a trainline monitor layup mode on a point-to-point communication network for a train.
2. Description of the Related Art
A train communication system developed by the assignee of the present application, based on the proposed European specification DIN 43322 for "Serial Interfaces to Programmable Electronic Equipment for Rail Vehicles," incorporated herein by reference, enables a master node located typically in a head car of a train to communicate via a serial bus to slave nodes on middle cars of the train and on a tail car of the train. See also, "International Standard-Information processing systems-Data communication-High-level data link control elements of procedures, ISO 4335", Third edition, Global Engineering Documents, Irvine, CA, 1987, the subject matter of which is also incorporated herein by reference.
The DIN 43322 using the ISO 4335 Standard provides for a train bus master to broadcast a "disconnect" command which completely shuts down a train bus by disconnecting the train bus from train bus slaves and the train bus master whenever that train bus master is keyed off by an operator. However, once the train bus is disabled, no communication can take place between the train bus master and the train bus slaves. Hence, once the train bus master is keyed off, the entire trainline monitor (TLM) system is disabled and no diagnostic or control information can be transmitted between the train bus master and a train bus slave.
This becomes particularly disadvantageous if the operator in the master car, i.e., the car which carries the train bus master, leaves that car unattended for only a short period of time, or if other maintenance personnel or cleaning personnel wish to activate auxiliary systems such as lights, air conditioning, heating or ventilation on any slave car, i.e., cars which carry train bus slaves, while the master car and consequently the train bus master is disconnected. In such cases, it would be desirable to provide a layup mode of operation in order to keep the auxiliary systems running for a finite period of time before completely shutting down the trainline system. This would both reduce wasted energy, and allow the maintenance and cleaning personnel to work in comfortable conditions rather than uncomfortably hot or cold conditions.
A problem that must be addressed in providing a layup mode occurs when a new train, or a new single car or a new group of cars are added to an original train while the train is in a layup mode. That is, since the train bus for the original train's trainline monitor system has not been disabled, a resultant trainline monitor system (comprising the original trainline monitor system and the newly added node) will likely have multiple train bus masters (master nodes). Hence, in order to provide a layup mode, the trainline monitor system for the resulting train must be capable of resolving multiple train bus masters to yield a single resultant train bus master for the resultant trainline monitor system problem while continuing to supply energy to all the cars on the resultant train.